This is the old United Nations University website. Visit the new site at

Contents - Previous - Next

Biogas generation: developments. problems, and tasks - an overview

E.J. DaSilva

Division of Scientific Research and Higher Education, Unesco, Paris, France


In recent years, biogas systems have attracted considerable attention as a promising approach to decentralized rural development. Developed and developing countries and several international organizations have shown interest in biogas systems with respect to various objectives: a renewable source of energy, biofertilizer, waste recycling, rural development, public health and hygiene, pollution control, environmental management, appropriate technology, and technical cooperation. Within the context of the UNEP/Unesco/ICRO microbiology programme, which is sponsored jointly by the United Nations Environment Programme, Unesco, and the International Cell Research Organization, several workshops have already been held in Yogyakarta, Manila, Mexico City, Singapore, and Bangkok, in an attempt to catalyze the applications of this acknowledged low-cost, nonwaste-producing technology that is increasingly being deployed to manage the environment and to ameliorate the search for substitute sources of fuel, food, and fertilizer (1 - 4). Early in 1979, in joint co" operation with IFIAS and ESCAP/UNIDO, a workshop will be held at Bandung to deal specifically with village micro" biology and the integrated biogas farming system. In this context, it is hoped that this activity on "The State of the Art of Bioconversion of Organic Residues for Rural Communities," a UN University joint World Hunger-Natural Resources activity receiving Unesco and UNEP/Unesco/ ICRO Panel support, will be making a significant contribution to the application of bioconversion processes for rural communities.

The utilization of microbial activity to treat agricultural, industrial, and domestic wastes has been common practice for a half century. Treatment includes the aerobic, activated sludge process and the anaerobic or methane fermentation method; the latter is simple, does not require imported know-how or components, is suited to small family or village-scale digestion, and is the only process utilizing waste as a valuable resource. Of great importance to the developing countries, the use of methane has, until recently, been restricted because of public antipathy or because other, cheaper energy sources were available. But, as can be seen from Tables 1 and 2, biogas technology today is a sufficiently significant producer of energy to command the attention of a fair number of countries (5) and agencies.

TABLE 1. Promotion of Research and Development Related to Use of Biogas

Place Sponsors of biogas research and development Number of plants Use of residual material and general remarks
Bangladesh Central government; Bangladesh

Academy for Rural Development


(under construction)

Meet fertilizer needs; develop co- operative or family-size biogas plants in rural area
China Local authorities 200,000(Szechuan) Family-size plants
Cook Islands Central government 1 (Roratonga) Integrated cattle farm with piggery pens; promote growth of algae and fish for production of protein
Ecuador Family co-operative effort in Iluman   Development of a biogas reactor to provide fuel for individual homes and a community bakery
Fiji Private enterprise 10 Rural development
India Government of India: All-India Co-ordinated Project 36,000 Target 100,000 units by 1978
Delhi Delhi Development Authority

Delhi Dairy Corporation

Indian Agricultural Research


Indian Institute of Technology


  Research on biogas reactor: design,

construction, and capacity

Pioneer in biogas research and


Research on biodegradable cellulosic


Haryana National Dairy Research Institute,


Mutuka Farm, Hatari village

12 12 plants (100 to 200 cu.ft.) operating

in Sonepat and Gurgaon districts

Uttar Pradesh Gobar Gas Research Station,


National Sugon Institute, Kanpur

National Livestock Development

Research and Extension Institute,

  Pioneer in biogas research and


Research on bagasse as substrate

10 plants (60 to 500 cu.ft.) operating

in the Deviapur and Kashipur districts


Gajarat Tulsi Shyam Temple, Una   3,000 cu.ft. plant in use for supply of

electricity only

Maharashtra National Environmental Engineering

Institute, Nagpur

Khadi and Village Industries


Gandhi Samarak Nidhi, Pune

National Dairy Research Institute,

Bombay (Regional Station)

Indian Institute of Technology,

Bombay (see also under Tamil Nadu)

  Research on insulator materials to

minimize heat losses in winter months

Pioneer in biogas research and


55 plants in operation using night soil

Has successfully experimented on

"integrated farming system" that yields

cattle fodder, fruits and vegetables

Deployment of biogas for diesel




Rural Electrification Corporation,


  4,500 cu.ft plant for community

development with technical assistance

from Council of Scientific and

Industrial Research

Orissa Central Rice Research Institute,


  Biogas production from Azolla crops
Tamil Nadu Indian Institute of Technology,

Madras (in collaboration with

I.I.T., Bombay and Indian Oil

Research Centre, Faridabad)

Shri A.M.M. Murugappa Chettiar

Research Centre

  Research in the use of biogas in petrol

kerosene and diesel engines

Development of low-cost materials for

biogas reactors

Pondicherry Auroville Ashram   Work in progress on inclusion of algae

in biogas system

Indonesia Dian Desa

Indonesian Board of Voluntary

Services, Development Technology

Centre, I.T.B., Bandung

12 Intensification of preliminary

programme;regional network proposed

for training and operation of biogas

plant processes

Japan Ministry of International Trade

and Industry (MITI); National

Institute of Animal Husbandry;

Bioconversion Committee of the

Agency of Industrial Science and

Technology; M/S Hitachi Plant

Construction Fermentation

Research Institute, Inage

  Pollution control biogas digestion

processes involve the use of

thermophilic micro-organisms

Korea (Republic of) Organization of Rural Development;

Institute of Agricultural Engineering

and Utilization, Suweon; Korea-U.K.

Farm Machinery Training Project

29,400 Production of food and fertilizer;

55,000 units planned by 1985

Nepal Development and Consultancy

Services, Butwal Technical Institute;

Energy Research and Development

Group; Tribhuvan University

10 200 units planned
Philippines National Institute of Science and

Technology; National Institute of

Animal Husbandry, Maya Farms,


100 Supports algal growth in

photosynthetic oxidation ponds;

irrigation of vegetable gardens

Thailand Agricultural Economic Dept.,


Division, Health Dept., Ministry of

Public Health; Mahidol University;

Kasetsart University; Applied Scientific

Research Corporation of Thailand

(MIRCEN - Microbiological Resources


225 50 digesters planned for every year

since 1975 for cooking and lighting


Upper Volta Services de Recherche et Applications

Techniques, Société Africaine

d'Etudes et de Développement

Research on development of biogas technology initiated
United Kingdom National Centre for Alternative

Technology, Wales

  Working demonstrations on methane


United States Biogas of Colorado, Inc., Denver   Development of a mobile

demonstration unit to generate biogas

for use in rural areas of Colorado.

Completed unit in corporates solar

temperature control system for use in


Emphasis is on simplicity of


Sri Lanka Industrial Development Board of the

Ministry of Industries

  100 regional centres planned; Rural

Energy Centre planned with UNEP to

meet the basic energy needs of a

village community (50 - 200 families)

Sources: S.K. Subramanian, Bio-Gas Systems in Asia, Management Development Institute, New Delhi, 1977; U.N. Agency documents.

TABLE 2. International Agencies Engaged in Biogas Research, Training, and Development Programmes

Agency Area Remarks
Economic and Social Commission

for Asia and the Pacific (ESCAP)

Examination of technological and

economic aspects (ESCAP projects on

biogas technology and utilization

supported by United Nations

Development Programme)

Workshops - Manila, New Delhi,

Bangkok, and (with Government of

Netherlands assistance),


FAO Agro-industrial residue utilization UNEP/FAO Seminar, "Residue

Utilization - Management of

Agricultural and Agro-Industrial

Wastes," Rome, 1977; information

available in FAO bulletins,

compendium of technologies, and

world directory of institutions

International Cell Research

Organization (ICRO)

Promotion of research and development
See under Unesco and UNEP/

of trained manpower

Unesco/ICRO Panel on Microbiology
International Development

Research Centre (IDRC)

Supports research designed to adapt

science and technology to the specific

needs of developing countries

IDRC Project Identification Meeting on

"Social and Economic Evaluation of

Biogas Technology," Sri Lanka, 1976

International Federation of Institutes

for Advanced Studies (IFIAS)

Identification and promotion of research

through commissioned studies

See under Unesco and UNEP/Unesco


Panel on Microbiology

Unesco Promotion of basic microbiological

research and development of trained


In collaboration with ICRO training

course on "Waste Recovery by

Micro-organisms" Kuala Lumpur,

1972, and with IFIAS, a

commissioned study on "Energy Self-

Sufficiency - A Feasible Prerequisite

for Self-Reliance"

UNEP/Unesco/ICRO Panel on

Microbiology in close co- operation

with UNEP, Unesco, ICRO, and IFIAS

Promotion of research in low-cost non-

waste- producing microbial technologies

and development of trained manpower

at established microbiological resources

centres (MlRCENs) at Bangkok, Cairo,

Nairobi, Porto Aiegre, and Stockholm.

Dissemination of information on micro-

organisms through the World Data

Centre at Brisbane

Training courses in Indonesia;

Thailand, The Philippines, Republic of

Korea, Kenya, Egypt, Mexico,

Guatemala, Singapore, Kuwait, New

Delhi, etc., on waste conversion and

environmental management using


United Nations Environment

Programme (UNEP)

Environmental management and

counteraction of pollution

UNEP Rural Energy Programme -

pilot projects in collaboration with

(i) Brace Research Institute, McGill

University, Canada: African Rural

Energy Centre at Senegal

(ii) Oklahoma State University, USA;

Asian Rural Energy Research Project,

Sri Lanka

(iii) Dissemination of information

through UNEP International Referral

System (IRS)

UNICEF Provision of basic services to children Studies on contributions of biogas

systems to village technology and rural


UNIDO Dissemination of information on biogas Proposed project: Biogas Plants -

assistance for the mobilization of

existing technology and its transfer

and integrated development

UNITAR Provision of specialized training Seminar on "Microbial Energy

Conversion," Gottingen, 1976

United Nations University (UNU) Counteraction of World Hunger (WHP)

Management of Natural Resources


Conference at INCAP with ICAITI on

"Bio-conversion of Organic Residues

for Rural Communities, November

1978, Guatemala

WHO Waste disposal and possible health


Preparation of monographs on

composting and on biogas utilizing

night soil

Sources: S.K. Subramanian, Bio-Gas Systems in Asia, Management Development Institute, New Delhi, 1977; U.N. Agency documents.

What is biogas?

Methane is the main constituent of what is popularly known as biogas. A colourless, odourless, inflammable gas, it has been referred to as sewerage gas, klar gas, marsh gas, refuse-derived fuel (RDF), sludge gas, will-o'-the-wisp of marsh lands, fool's fire, gobar gas (cow dung gas), bioenergy, and "fuel of the future." The gas mixture produced is composed roughly of 65 per cent CH4, 30 per cent CO2, and 1 per cent H2S. A thousand cubic feet of processed biogas is equivalent to 600 cubic feet of natural gas, 6.4 gallons of butane, 5.2 gallons of gasoline, or 4.6 gallons of diesel oil. For cooking and lighting, a family of four would consume 150 cubic feet of biogas per day, an amount that is easily generated from the family's night soil and the dung of three cows. In addition, rural housewives using the biofuel are spared the irritating smoke resulting from the combustion of firewood, cattle dung cakes, and the detritus of raw vegetables (Figure 1).

Figure. 1. The Attributes of Biogas as a Fuel vs. the Disadvantages of Wood (Source: Bio-Gas Newsletter, August 1976)

Microbiology of CH4, or bio-methanogenesis

Anaerobic digestion technology or the methane-generating bioconversion yields both fuel (biogas) and organic fertilizer (sludge), products that are the final result of microbial action on cellulosic and other non-chemically processed organic residues. These substrates are obtained through a series of degradative steps that involve a variety of bacteria (6 11). In the first step, complex polymeric organic substrates - proteins, carbohydrates, and fats - are transformed by non-methanogenic bacteria into essentially non-methanogenic substrates like butyrate, propionate, lactate, and alcohol. Through a second step that involves the acetogenic bacteria, the composition and identity of which still remain to be determined, these compounds are transformed into methanogenic substrates, i.e., acetate, H2 and C1 compounds that are converted into CH4 and CO2 by the methane bacteria, obligate anaerobes that multiply in a neutral or slightly alkaline environment.

That the smooth cooperation of the three groups of bacteria has to be well regulated is exemplified by Bryant's discovery (12) of two mutually inter-dependent species existing in a symbiotic association that was formerly considered a pure culture under the name of Methanobacillus omelianskii. The association is comprised of two symbionts: an acetogenic organism and a methanogenic organism. The acetogen produces acetate and H2 and CO2, thereby disrupting the process of auto-inhibition with the acetogen, which succumbs to the H2 it produces.

Again, it is necessary that both aspects of the anaerobic digestion process - liquefaction and gasification - be well balanced. If the methane bacteria are absent, the digestion process may only succeed in liquefying the material and may render it more offensive than the original material. On the other hand, if liquefaction occurs at a faster rate than gasification, the resultant accumulation of acids may inhibit the methane bacteria and the bioconversion process as well.

Contents - Previous - Next